Conductor compositions applied to and fired on dielectric substrates (glass, glass-ceramic, and ceramic) usually comprise finely divided inorganic powders (e.g., metal particles and binder particles) and are commonly applied to substrates using so-called "thick-film" techniques as a dispersion of inorganic powders in an inert organic liquid medium or vehicle. Upon firing or sintering of the printed film, the metallic component of the composition provides the functional (conductive) utility while the inorganic binder (for example, glass, B.sub.2 O.sub.3, etc.) bonds the metal particles to one another and to the substrate. Thick film techniques are contrasted with thin film techniques involving deposition of particles by evaporation or sputtering. Thick film techniques are discussed in "Handbook of Materials and Processes for Electronics", C. A. Harper, editor, McGraw-Hill, New York, 1970, Chapter 12.
The most commonly used conductor compositions employ noble metals, especially gold, silver, platinum, palladium, and their mixtures, alloys and compounds, since their relatively inert characteristics permit firing in air. Attempts at using dispersions of less expensive non-noble metals have often been confined to specialized uses or have required the great practical inconvenience and expense of firing in nonoxidizing atmospheres (nitrogen, nitrogen/hydrogen, hydrogen, argon, etc.).
There is a distinct commerical need for less expensive conductor compositions which can be fired in air to produce adherent low resistivity conductors on dielectric substrates.
In particular there is a need for a composition that can be used as the busbar to the tin oxide anode of a DC-gas discharge display. Such a composition should be inexpensive, fireable in air, physically and chemically compatible with plain and tin oxide coated soda lime glass, exhibit good adhesion and yield good humidity resistance. Of the various possible candidates, silver requires a dielectric coating to prevent reaction between it and the mercury in the gas atmosphere of the display. This contributes to a higher fabrication cost. Fired aluminum compositions exhibit too high a resistivity and copper compositions require firing in an inert atmosphere. West German published application number 2,803,926 discloses an improved composition based on the addition of elemental silicon to an aluminum composition. Although the disclosed compositions give good properties when fired at 605.degree. C. and above, no details are given for firing at 600.degree. C. and below. Since planar gas discharge displays are generally fabricated using unsupported soda lime glass substrates, it is desirable to carry out the firing operation at temperatures less than 600.degree. C. to prevent sagging of the substrate.